world meteorological · web view1.2 entering into the 21st century, in line with the...

WORLD METEOROLOGICAL ORGANIZATION_______________________________

JOİNT MEETİNG OFCBS EXPERT TEAM ON SURFACE-BASED

REMOTELY-SENSED OBSERVATİONS(First Session)

AND

CIMO EXPERT TEAM ON REMOTE SENSİNGUPPER-AİR TECHNOLOGY AND TECHNİQUES

(Second Session)

GENEVA, SWITZERLAND, 23-27 NOVEMBER 2009

CBS-CIMO Remote Sensing/Doc. 2.4

(17.XI.2009) ______

ITEM: 2.4

Original: ENGLISH ONLY

ASSESS THE CURRENT AND POTENTIAL CAPABILITIES OF WEATHER RADARS FOR THE USE IN WMO INTEGRATED GLOBAL OBSERVERING

SYSTEM (WIGOS)

Assess the status/plans of implementation for weather radars by WMO Members in relation to meeting user requirements for all application areas and provide updates to

the WMO CEOS of observations systems capabilities database as necessary

(Submitted by Ercan Büyükbaş, Turkish State Meteorological Service (TSMS))

Summary and Purpose of Document

This document presents the status of implementation of weather radars by WMO members and provide recommendations for activities that should be carried out under the auspice of WMO.

ACTION PROPOSED

The meeting is invited to note the information contained in this document in identifying activities to be carried out to meet user requirements for all application areas in the context of the Rolling Review of Requirements of the GOS. The meeting will also be invited to develop guidance material for providing updates of the WMO CEOS of observations systems capabilities database.

_________________

http://www.wmo.int/pages/prog/www/IMOP/meetings.html

http://www.wmo.int/pages/prog/www/IMOP/meetings.html

CBS-CIMO Remote Sensing/Doc. 2.4, p. 2

1. INTRODUCTION

1.1 From the early stage of the history until today human being have been interested in the atmosphere and weather phenomena for both observing the existing situation and predicting its changes for future. In this context, a lot of studies have been performed during the history to develop methods, instruments, systems and models for improving the quality of the weather observations and forecasts to fulfil the meteorological requirements with the maximum benefits for the users.

1.2 Entering into the 21st century, in line with the continuously increasing needs of the developing world and varying demands of the different sectors, it is very obvious that there is a necessity for the provision of accurate and timely weather observations which will be the essential input of meteorological services and studies such as weather forecasts and numerical weather prediction models, research studies on climate and climate change, sustainable development, environment protection, renewable energy sources, etc. All outputs and products of any system are input dependant. So, accuracy, reliability and efficiency of the products of any meteorological study will depend on its input: Observation.

1.3 It is getting more important and vital to observe the weather and to make weather prediction timely especially for severe weather conditions to be able to warn the public in due course. One of the most important and critical instruments developed and offered by the modern technology for observing weather is weather radar.

1.4 The term RADAR as the abbreviation of RAdio Detection And Ranging was first used by the U.S. Navy in 1940 and adopted universally in 1943. It was originally called Radio Direction Finding (R.D.F.) in England.

1.5 Operation principle of a radar is very simple in theory. Radar emits a radio signal in a certain frequency into its surroundings and receives the reflected signal from any object. After the processing of this signal, the distance, type, shape, size and motion of the object can be estimated based on the strength and frequency shift of the returned signal. The returned signal (echo) from any target measured by the radar is generally called as "reflectivity“. Reflectivity magnitude is related to the number and size of the objects encountered.

1.6 Although the starting of the research and development studies for radars are dated to the first half of 1800s, the radars have been used for tracking the weather systems since early 1950s, after the 2nd World War. Radars with the capability of the reflectivity measurements only were put into operation for the detection and tracking of weather phenomena such as thunderstorms and cyclones with limited moving target indication capability.

1.7 After 1970s, by the development of the Doppler technology, it would be possible to get the velocity and direction information of the meteorological targets more accurately as well as the intensity and location of them.

1.8 In addition to the Doppler technology, the researches on the polarimetric radars since late 1990s have brought out new approaches and opportunities for radar operations, particularly for hail detection and hydrometeor classification, and dual polarization technology has been put into operational use after 2000s with new features and benefits for users. These new benefits provided by dual polarization radars urge the radar users either to upgrade the existing systems for dual polarization features or to have new systems with this capability. Furthermore, advanced signal processing and data processing methods have also increased the capability of the weather radars significantly.


2. MAIN UTILIZATIONS OF WEATHER RADARS

2.1 Although the hydrometeors in the atmosphere as the main targets for weather radars vary from the very small particles of non-precipitation clouds to big hail drops, radars are capable of detecting and classifying them. On the other hand, non meteorological targets such as birds, insect and dust clouds can also be detected by weather radars.

2.2 It will not be wrong to assert that weather radars as active remote sensing systems, at least for today, are the only and essential instruments as active remote sensing systems which can provide real time (less than 15 minutes depending on the scanning strategy and processing features), accurate and high resolution (up to 150 m) weather information in large scale area (up to 500 km depending on the frequency used) particularly for nowcasting purposes.

2.3 Some researches and inquiries showed that main utilizations of weather radars for meteorological services could be listed as below in the order of the priority:

1. Large scale weather monitoring

2. Nowcasting and early warning

3. Flood warning

4. Tornado warning

5. Aviation safety

6. Wind warning

7. Hail detection

8. Others (hydrology, general warnings for public, research, weather modification, etc.)

2.4 Although the short list above demonstrates that weather radars are used mainly for preparing the warnings against severe weather conditions, they can provide many information and products for several purposes with the capabilities summarized below:

a) Determination of time, quantity and location of the precipitation occurred,

b) Estimation of time, quantity and location of expected precipitation,

c) Tracking the weather systems by estimating the intensity, direction and velocity,

d) Providing real time data for numerical weather prediction models as well as hydrological forecasting models,

e) Supporting weather modification studies,

f) Identification of precipitation type (hydrometeor classification),

g) Supporting the disaster management and hazard mitigation activities by means of early warnings against hazardous heavy rain, flash flood, hail, strong wind, tornado, hurricane, etc.

h) Improving the aviation safety by means of en-route surveillance,

i) Supporting marine meteorology and road meteorology services,

j) Determination of wind shear, microburst, macroburst, downburst and strong winds with spatial, temporal and vectoral information at the airports and flight regions (by using TDWR particularly),

k) Real time monitoring of the location, surface and travelling of cold and warm fronts,


l) Determination of the wind components as spatial, temporal and vectoral in any place for a certain time,

m) Determination and monitoring of forest fires,

n) Determination and monitoring of the air polluted areas particularly in winter times,

o) Tracking the birds in flight, and dust and insect clouds.

3. WEATHER RADAR TYPES

3.1 Weather radars used by WMO members may be classified in several ways due to the criteria of the classification, e.g. receiving and transmitting type, operating frequency band, polarization type, type of transmitter, Doppler, non-Doppler, etc. The most common classification and types are described briefly in this part.

3.1 Frequency Bands of Weather Radars

3.1.1 Generally, weather radars are classified by the frequency band used. The mostly used weather radars are C-Band , S-Band and X-Band radars respectively. Although their use is very rare, L-Band and K-Band weather radars are also available for specific purposes.

3.1.2 The radar bands located in the spectrum are shown below:

Table 3.1. Radar Bands

3.1.3 Specific frequencies within above ranges have been assigned for radars by International Telecommunication Union (ITU). The radio frequency bands used by weather radars are located around 1.2-1.4 GHz (L-Band), 2.7-2.9 GHz (S-Band), 5.6-5.65 GHz (C-Band), 9.3-9.5 GHz (X-Band) and 35.2-36 GHz (Ka-Band).

a) S-band radarsThose radars operate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation. It requires a large antenna dish and a large motor to power it. S-Band radars are generally used to detect and track severe weather phenomena in long ranges such as tornado, hurricane, etc.

Band Designation Nominal Frequency Nominal WavelengthHF 3-30 MHz 100-10 mVHF 30-300 MHz 10-1 mUHF 300-1000 MHz 1-0.3 mL 1-2 GHz 30-15 cmS 2-4 GHz 15-8 cmC 4-8 GHz 8-4 cmX 8-12 GHz 4-2.5 cmKu 12-18 GHz 2.5-1.7 cmK 18-27 GHz 1.7-1.2 cmKa 27-40 GHz 1.2-0.75 cmV 40-75 GHz 0.75-0.40 cmW 75-110 GHz 0.40-0.27 cmMm 110-300 GHz 0.27-0.1 cm


b) C-band radarsThose radars operate on a wavelength of 4-8 cm and a frequency of 4-8 GHz. The signal is more easily attenuated, so this type of radar is best used for short range weather observation. Also, due to the small size of the radar, it can therefore be portable. The frequency allows C band radars to create a smaller beam width using a smaller dish. C band radars also do not require as much power as an S band radar. C-Band radars are very suitable for precipitation measurements. The new developments on polarimetry have made them very capable for hydrometeor classification.

c) X-band radarsThose radars operate on a wavelength of 2.5-4 cm and a frequency of 8-12 GHz. Because of the smaller wavelength, the X band radar is more sensitive and can detect smaller particles. These radars are used for studies on cloud development because they can detect the tiny water particles and also used to detect light precipitation. X band radars also attenuate very easily, so they are used for only very short range weather observation. Most of the terminal Doppler weather radars are chosen as X-Band radars by considering their structure and features. Furthermore, X-Band is very suitable for mobile radar applications.

S-Band Radars C-Band Radars X-Band Radars

FREQUENCY 2-4 GHz(2.9 GHz)

4-8 GHz(5.6 GHz)

8-12 GHz(9.3 GHz)

WAVE LENGTH 15-7.5 cm(10.3 cm)

7.5-3.8 cm(5.3 cm)

3.8-2.5 cm(3.2 cm)

TYPICAL RANGE 300-500 km 120-240 km 50-100 km

PEAK POWER 500 kW- 1MW(750 kW)

250-500 kW(250 kW)

50-200 kW(200 kW)

MEASURING SENSITIVITY

Rain, snow, hail (The bigger particles as compared to

C-Band)

Rain, snow, hail, drizzle (The bigger

particles as compared to

X-Band)

Rain, snow, hail, light drizzle (The smaller

particles as compared to S-Band and

C-Band)

ATMOSPHERIC ATTENUATION

Less attenuation as compared to C-

Band and X-Band

Less attenuation as compared to X-

Band while much attenuation as

compared to S-Band

Much attenuation as compared to C-Band

and S-Band

ANTENNA SIZE(1 deg. beam

width)7.5 m 4.2 m 2.5 m

COST 1.5x C-Band2x X-Band

0.7x S-Band1.3x X-Band

0.5x S-Band0.8x C-Band

Table 3.2. A roughly comparison of 3 types weather radars mostly used


3.2 Non-Doppler Weather Radars and Doppler Weather Radars

a) Non-Doppler Weather RadarsThese types of weather radar are called as “conventional weather radars”. Non-Doppler radars can make the reflectivity measurements to estimate the distance and intensity of the targets with limited capability for moving target indication by using some clutter suppression algorithms. Most of the weather radars used by WMO members before 1990s were the conventional weather radars.

b) Doppler weather radarsDoppler weather radars are capable of obtaining information about the velocity, direction and strength of the targets by using Doppler effect and advanced processing algorithms as well. If a target is moving relative to radar, this will cause a change in the frequency of received signal proportional to the amount of the movement. This is called as Doppler Effect or Doppler Shift and velocity of the target can be calculated by using this information. Today, all of the radars have been manufactured with Doppler capability to meet the requirements of meteorological services.

3.3 Single Polarization Radars and Polarimetric Radars

a) Single Polarization Weather RadarsElectromagnetic or radio waves consist of electric (E) and magnetic (H) force fields, which are perpendicular to each other and to the direction of propagation of the wave front, propagate through space at the speed of light. Electric and magnetic fields are always perpendicular to each other. So, it is possible to specify the orientation of the electromagnetic radiation by specifying the orientation of one of those fields.

Figure 3.1. Propagation of electromagnetic waves

3.3.1 Most of the weather radars use the linear horizontal polarization by considering that it performs very well to detect the main weather targets based on the suitability of their shapes and distribution.


b) Polarimetric RadarsMost weather radars transmit and receive radio waves with a single horizontal polarization. That is, the direction of the electric field wave crest is aligned along the horizontal axis. Polarimetric radars, on the other hand, transmit and receive both horizontal and vertical polarizations. Since polarimetric radars transmit and receive two polarizations of radio waves, they are sometimes referred to as dual-polarization radars.

3.3.2 Polarimetric Doppler Weather Radars are getting more popular because they improve the accuracy of quantitative precipitation measurement and hydrometeor classification significantly with additional transmitting and processing functionality allowing further information on the directionality of the reflected electromagnetic energy received.

4. BASIC PRODUCTS OF WEATHER RADARS

4.1 Basic Radar Parameters

4.1.1 Weather radars can provide a lot of information and products for several purposes by means of measuring or deriving basic radar parameters below:

Z = Reflectivity (dBZ)V = Radial Velocity (m/sec)W =Spectral Width (m/sec)R = Rainfall Rate (mm/h)

4.1.2 On the other hand, the following parameters can be obtained from dual polarization radars:

1. Horizontal Polarization Reflectivity ( ZH)2. Vertical Polarization Reflectivity ( ZV)3. Differential Reflectivity (ZDR)4. Radial Velocity (V) 5. Spectral Width (W)6. Precipitation Amount ( R)7. Polarimetric-Correlation Coefficient (ρHV)8. Differential Phase Shift (ØDP)9. Specific Differential Phase (KDP)

10. Linear Depolarization Ratio (LDR)

4.2 Weather Radar Products

4.2.1 Although there may be different nomenclature, definitions and classifications by the different manufacturers and users, the products generated by weather radars which can be used very efficiently by WMO members are described as below:

a) Basic Productsb) Rainfall Products/Hydrological Productsc) Wind Productsd) Dual Polarization Products e) Forecast and Warning Productsf) Composite Products

4.2.2 These products can be converted in different formats such as NEXRAD Level1 and Level2, WMO FM 92-IX Ext GRIB1 and GRIB2 (GRid In Binary), WMO FM-94 BUFR edition 1, 2 and 3 (Binary Universal Form Representation), HDF5, GEOTIFF, TIFF, JPG, PNG, GIF, BMP, Postscript, and transmitted to anywhere as required.


a) Basic Products

1. Plan Position Indicator (PPI) 2. Range Height Indicator (RHI)3. Constant Altitude Plan Position Indicator (CAPPI)4. Pseudo CAPPI (PCAPPI) 5. Maximum Display 6. Echo Top Height 7. Echo Base Height 8. Vertical Wind Profile (Volume Velocity Processing-VVP)9. Height of Maximum Intensity

b) Rainfall Products/Hydrological Products

1. Surface Rainfall Intensity (SRI) – R (mm/hr). 2. Rainfall Intensity Histogram 3. Surface Precipitation Accumulation (mm) 4. Subcatchment Accumulation (mm) 5. Vertically Integrated Liquid (VIL) – (mm)6. Vertically Integrated Liquid Density – (grm-3)

c) Wind Products

1. Radial Shear – msec-1/km2. Azimuthal Shear – msec-1/km3. Elevation Shear - msec-1/km4. Radial-Elevation Shear - msec-1/km5. Radial-Azimuth Shear - msec-1/km6. Radial-Azimuth-Elevation Shear - msec-1/km7. Horizontal Shear - msec-1/km8. Vertical Shear - msec-1/km9. Shear Line10. Three Dimensional Shear - msec-1/km11. Layer Turbulence – W12. Storm Relative Velocity – msec-113. Horizontal Wind Speed and Direction – V

14. Velocity Azimuth Display – V

d) Dual Polarization Products

1. Rainfall Rate Estimationa. R (Zh,Zdr)b. R (Kdp)c. R (Kdp,Zdr)

2. Hydrometeor Classification Product, a. Dry Snow-DS b. Wet Snow-WS, c. Stratiform Rainfall-SR, d. Convective Rainfall-CR, e. Hail-HA, f. Graupel-GR, g. Non-meteorological echo-NM,

3. Precipitation Efficiency Rate product:a. Light Precipitation-LP,b. Moderate Precipitation-MP,


c. Heavy Precipitation-HP,d. Large Drops-LD,

e) Forecast and Warning Products

1. Microburst product2. Gust Front forecasting product3. Hail Detection product4. Cell Tracking products5. Mezosyclon Detection product

f) Composite Products

The composite products can be generated by combining the data from different radars in the network. These products can be used efficiently by the forecasters to make an overall interpretation and comparison of data from different radars for a more accurate forecasting.

5. OVERVIEW OF WEATHER RADARS USED BY WMO MEMBERS

5.1 Type and Number of Weather Radars

5.1.1 The sources on weather radar literature state that weather radars have been used since 1950s. From that time until today, the number, type, feature and use of weather radars increased in a considerable amount.

5.1.2 The following tables have been prepared to show the historical process of weather radars used by WMO members including number and types of the radars. It must be keep in mind that these figures may not represent the actual numbers and types of the weather radars in used by WMO members because the lack of the information from all members. Similar to the operation of weather radars, we tried to scan our coverage area as much as possible by reviewing the previous reports published by WMO, examining web site of members, recent installation reports from prime manufacturers and using the information received from the representatives of WMO members during the international seminars, conferences and training activities. Although it is very obvious that there is still some gap about the weather radars used by WMO members, following figures may give a general view, at least a good estimation, for the use of weather radars from past to today. This information may also help to evaluate the existing situation and to envisage the future needs and developments.


Table 5.1. Weather Radars Used by WMO Members

Table 5.8. Weather Radars in Regions (2009)


Table 5.2. Weather Radars in RA I (2009)

Table 5.3. Weather Radars in RA II (2009)


Table 5.4. Weather Radars in RA III (2009)

Table 5.5. Weather Radars in RA IV (2009)


Table 5.6. Weather Radars in RA V (2009)

Table 5.7. Weather Radars in RA VI (2009)


5.2 Basic Characteristics of Weather Radars Used by WMO Members

a) Total number of known weather radars operated by WMO members are 1043 with the following types:

368 S-Band (35%) 503 C-Band (48%) 172 X-Band (17%) 705 Doppler (68%) 338 Non-Doppler (32%) (conventional).

b) In recent years there is an important intention to polarimetric radars because of the very useful and efficient products and features. It has been reported that there are 39 polarimetric radars in operational use. Most of them, 30 out of 39, are in Region VI.

c) Although there is no detailed information about the quantities of the transmitter type of the weather radars, it is estimated that majority of the transmitters are magnetron type. Recently, by considering the coherency requirements for more accurate Doppler measurements, some countries have been preferring klystron transmitters although they are more expensive than those magnetron ones. Travelling Wave Tubes (TWT) and solid state power amplifiers are the other options rarely used for generating the power for transmitter.

d) More than 50 members of WMO have been exchanging radar data with other countries via GTS or internet as member of regional networks or bilateral and multilateral cooperation.

e) Main communication medias for the data transmission between remote radar sites and radar operation centres are terrestrial line and radio link. A few countries use satellite based communication network.

5.3 Regional Weather Radar Networks

5.3.1 Based on the importance of the weather radar data for not only local area but also regional and international scale, regional weather radar networks have been established for a better and cost-effective operation in order to provide the best service to the users. There are some networking and data exchanging attempts in Europe, Scandinavia, Baltic, Caribbean Islands, Central America and South-East Asia.

5.3.2 Such regional networks play very important roles for improving the capacity of the members and efficiency of weather radars:

a) They can provide information for a very large area by exchanging data,

b) The gaps of local or national networks can be covered by regional networking,

c) The cost for investment and operation of the systems can be reduced by sharing them as well as avoiding the duplication for some costs,

d) The spares and consumables can be provided jointly with a cost-effective approach,

e) The validation and calibration of radar data can be made more accurately,

f) They can also support each other for validation as well as back-up for the intersection areas,

g) They can give opportunities to share the experiences for a better service and operation, particularly improvement of quality and timeliness of warning capability,


h) The new developments in the technology can be followed and integrated to the systems,

i) The standards for the products and operations can be developed,

j) They provide a proper platform for the innovation of new products and algorithms,

k) Different solutions can be developed for meeting the requirements by regional and international cooperation activities,

The brief information about some of such networks and projects are given below:

a) OPERA

Following COST 72 (European Cooperation in the Field of Scientific and Technical Research) and COST 73 projects sponsored by European Economic Community (EEC) for the establishing an integrated weather radar network for European countries, OPERA (Operational Program on the Exchange of Weather Radar Information) was established in 1999 as a programme of EUMETNET (The Network of European Meteorological Services) in order to harmonise and improve the operational exchange of weather radar information between National Meteorological Services in Europe.

After the completion of OPERA-1 (1999-2003) and OPERA-2 (2004-2006), OPERA-3 (2007-2011) has been put into the implementation as the third phase to firmly establish the program as the host of the European Weather Radar Network with participation of 29 European countries. European radar network involved in OPERA consists of 32 S-Band, 157 C-Band and 1 X-Band radar.

Figure 5.1 European Weather Radar Network (OPERA)


b) NORDRADNordic Weather Radar Network (NORDRAD) is a network established to exchange the weather radar data between the participant countries. Finland, Norway, Sweden, Estonia and Latvia are the partners of the organization and they operate 32 C-Band weather radars totally.

c) CARIBBEAN WEATHER RADAR NETWORKCaribbean weather radar network project is still under implementation as a regional project funded by European Union. It is proposed that 4 radars in Trinidad Tobago, Belize, Barbados and Guyana shall be installed within the scope of the project under coordination of Caribbean Meteorological Organization. The existing radars in Jamaica, the Dominican Republic, Guadeloupe, Martinique and French Guyana and these new four radars are planned to be integrated to form a radar network of 9 radars covering Caribbean Islands for providing more accurate and timely information on all kinds of severe weather.

d) BALTRADBALTRAD is a regional weather radar networking project to create an advanced weather radar network for the BSR, as a durable and sustainable element of regional infrastructure. It has been declared that the Project with the partnerships as Sweden, Finland, Poland, Latvia, Denmark, Belarus, and Estonia proposes:

exchange of polar data among all members of the Partnership

a weather radar data exchange framework fully compliant and preferably integrated with the WMO Information System (WIS)

a common production framework containing harmonized algorithms, including those employing dual-polarization data

consistent end-to-end management of quality information

a software system which is available according to Open Source principles.

6. CONCLUSION

The evaluations and comments in general based on the information collected from different sources about the weather radars and their use by WMO members are as follows:

6.1 Current Status

a. As a result of above mentioned unique features of the weather radars, most of the meteorological services have been either installing or upgrading the Doppler weather radars increasingly to improve the capabilities of their early warning systems against the severe weather phenomena such as heavy rain, strong wind, tornado, hail, etc.

b. Furthermore numerical weather prediction models, weather modifications applications and research studies in many areas need weather radar data which force the meteorological services to have weather radars systems and operate efficiently.

c. It seems that more than 80 out of 182 members of WMO have been operating weather radars. It has been observed that weather radars have mainly used by developed countries due to the high investment and operating cost of the radars. Recently, developing countries have also been showing a high interest for making weather radar investments. But it is certain that real number of weather radars operated by WMO members is more than this figure. Furthermore, it is known that some other agencies rather than WMO members have also been operating a large


number of weather radars. It means that number of weather radars in operation may be much more than the reported ones.

d. Major radar types used by WMO members are S-Band, C-Band and X-Band radars. The choice of the radar type basically depends on the type, severity and distance of weather phenomena to be detected. For example, the countries near by oceans exposed to severe weather phenomena such as hurricane, tornado, hail storm, tropical siclon, etc. prefer S-Band radars while the countries are not suffered such phenomena but interested in precipitation measurements and flood warning prefer C-Band radars.

e. Maintenance of the weather radars have been made by the own technical staff in most of the member countries. A few country transfers this responsibility to third parties (manufacturers or local maintenance companies) by means of maintenance contract.

f. Generally, rain gauge data have been used for the validation and calibration of weather radars. Recently, disdrometers have been proposed to use for the validation and calibration studies with a view that disdrometers will allow real time measurement of rainfall dropsize distributions for calibration of the Z-R relationship between radar reflectivity and rain rate.

g. Maintenance of the systems, supplying required spare parts cost and timeliness point of view, lack of qualified staff for maintenance, operation and product interpretation are the problems encountered for the operation weather radars.

h. It has come out from our searches that lightning seems to be the most dangerous and hazardous event for weather radar sites. The general method for the protection is to use lightning rod connected to the grounding system. An effective lightning protection and grounding system should be designed and installed based on a very detailed analysis of the site conditions. These protection systems should include surge protectors/absorbers.

6.2 Future plans

a) It is not easy to make detailed and specific assessment about the future plans of the member countries without receiving the information directly from the authorities of the members. But some general issues can be highlighted based on the information available, general trend and innovations in the field of the weather radars as well as the requirements and expectations from meteorological services.

b) Based on the information collected, we can say that Seychelles, South Africa, Sudan from RA I; Bangladesh, China, Hong-Kong, India, Iran, Japan, Korea, Pakistan, Saudi Arabia, Thailand, Turkmenistan, United Arab Emirates, Uzbekistan from RA II; Argentina, Brazil from RA III; Barbados, Belize, Canada, Guatemala, Guyana, Honduras, Trinidad Tobago, USA from RA IV; Australia, Indonesia, Malaysia, New Zealand from RA V; Austria, Belarus, Bulgaria, Cyprus, Estonia, Finland, France, Germany, Hungary, Jordan, Latvia, Poland, Russia, Serbia, Spain, Sweden, Turkey, United Kingdom from RA VI have some plans to establish new weather radars or to upgrade the existing ones.

c) It has been understood from our studies that the upgrade plans include hardware and software upgrade for having Doppler capability, dual polarization, advanced signal and data processing tools and methods, developed application software for product generation and dissemination, networking, remote monitoring and maintenance function, etc.

d) It can be concluded that developed, developing and less developed countries intend to use weather radar data to perform their tasks more efficiently and they would like to have weather radars if they do not have already, or they would like to improve their capabilities by adding new radars or upgrading existing systems.


e) Since early 1990s Doppler capability has become a standard feature for all weather radars. Similar to the process for Doppler capability, it seems that dual polarization which has come up a new and useful feature for weather radars will become also a standard feature for weather radars. The members who are interested in hydrometeor identification and more accurate quantitative precipitation measurements would like to have weather radars with this new and unique capability.

f) Although it is a very useful instrument for meteorologists, to install and operate weather radars are very expensive. This is why it seems that some countries may not be in a position from financial aspect to make such investments due to the lack of sufficient resources. Less developed and developing countries may need funding from international organizations or developed countries to be able to execute radar investments. Consequently, international cooperation and funding mechanism should support them to have required systems.

g) Weather radar investments are very expensive and critical with the need of sufficient budget as well as experts for the operation. This is why all issues regarding the operation of the radar network should be evaluated by considering the data and services expected from radar network. It is strongly recommended to make a feasibility study including meteorological evaluation, e.g. analysis of the rainfall and flood producing weather systems, radar coverage, big settlements areas, existing infrastructure and the requirements, communication options for data transmission, power requirements and availability, maintenance options, etc. to be able to design proper system for the requirements.

h) In addition, electromagnetic compatibility (EMC) analysis should be performed to determine the suitability of the site on the basis of interference between the radar and other types of radio/radar services, and human exposure to the transmitted radar beam. Such analysis should identify the operating frequency and the power of the radar.

i) By considering the sharing radar bands with other radio services, the protection criteria for weather radars developed by ITU-R and reported by WMO should be followed. Considering the increasing demands of frequency allocation for high speed data transmission by using wireless technology for remote access to required systems, ITU has allocated 3 bands for the use of Radio Local Area Network (RLAN). These bands are 2.4 GHz (2.4-2.4835 GHz), lower 5 GHz (5.15-5.35 GHz) and higher 5 GHz (5.47-5.725 GHz). It seems that the third one (5.47-5.725) is critical for weather radar operations particularly by considering that 5.6-5.65 GHz band is used by weather radars. Although ITU’s has made this allocation with the basis of non-interfering with weather radars, it has been reported by some WMO members that RLAN equipment interfere their weather radars with very harmful effect. Dynamic frequency selection (DFS) is mandatory for all RLAN equipment to avoid such interferences. Under DFS, RLANs have to monitor their channel and, if they detect a radar signal, they have to move to another channel. But it is understood from the reports that DFS has not providing sufficient protection for the weather radars. This is why necessary precautions should be taken efficiently by the RLAN users to avoid the interference. Related teams of CIMO and CBS should collaborate with WMO-Steering Group on Radio Frequency Coordination (SG-RFC) to develop solutions for this problem to discuss with the other parties, i.e. ITU, RLAN users and RLAN equipment manufacturers.

j) On the other hand, the precautions for effective interference mitigation should be discussed with local frequency management authority and weather radar supplier before the implementation of radar Project. In case of occurrence of such a problem during the operation of radars, a proper solution should be found by discussion related parties.


k) WMO members should take into consideration that well trained operators and engineers are needed for operating the weather radars as well as well trained meteorologists for interpreting the radar products to provide required meteorological services. This is why national and international capacity building activities such as workshops, seminars and trainings should be organized to improve the capabilities of member countries.

l) Furthermore, a common standard for the basic requirements of weather radars to be developed by expert teams of WMO would be very helpful for establishing and/or upgrading the weather radars as well as for operating the weather radars smoothly. These standards should include basic features of the instruments and basic products to be generated.

m) Another important issue to be considered and studied to benefit from weather radars is assimilation of weather radar data for numerical weather prediction models to have more accurate products from these models. The trainings and seminars on this subject should be organized for the counties which has not expertise on this subject.

n) A guideline including methods and algorithms can be developed for validation and calibration of weather radar data which would be a common standard for all users. The cooperation between the members for the radar calibration should be encouraged and supported by WMO.

o) By considering the importance of weather radar observations for many meteorological purposes, particularly for weather forecasting, it has been emphasized strongly in many of reports by WMO that members are invited to establish and maintain weather radars and exchange the weather radar data on a bilateral era multilateral basis. On the other hand regional and sub-regional collaborations have also been encouraged and supported by WMO.

p) We have deduced from our studies that most of the members keen on having weather radars, exchanging weather radar data and participating in regional networks. Establishing regional networking, e.g. OPERA as a good application example, should also be encouraged and supported. A worldwide weather radar network may be established by combining the regional networks for the benefits of all members. WMO may develop procedures including methods, formats and algorithms for making the data exchange easier for the members.

7. REFERENCES

1. Rinehart, Ronald. E.- Radar for Meteorologists, 19972. Skolnik, Merill I.-Radar Handbook, 3. Doviak R.J. and Zrnic D.S.-Doppler Radar and Weather Observations 4. Croci, R.-Radar Basics, 5. Gilet, M.-Information on Weather Radars Used by Members, WMO, 19896. Feasibility Report on Hydrometric Network Review, Design And Automated Weather And -

Hydrometric System Design for Turkey-TEFER Project, BoM, 20007. Hart, T.- Report from the Rapporteur on Regional Aspects of the Global Obs. System,

WMO, 20018. Reference List of Manufacturers for Weather Radars, 2001 9. Report of the Gos in Region II, WMO, 200210. Franc, D.-Interference Protection criteria for meteorological radars, WMO, 200211. Report on Weather Radar Operation in JMA, WMO, 2002 12. Handbook, Use of Radio Spectrum for Meteorology, WMO-ITU, 2002, 13. Weather Radar Training Document and User Manuel- Mitsubishi Electric Corp. ,200214. Report on RA VI Meeting of the Working Group on Planning and Implementation of WWW

Co-Ordinators, WMO, 200315. Report on Regional Aspects of the WWW Components, PWS Programme and Support

Functions, Including Reports by the Co-Ordinators, WMO, 200416. Manual on the Global Observing System, WMO, 2004


17. Weather Watch Radar, BoM, Australia, 200418. Eminoglu, S.-Notes on Radar Basics, TSMS, 200419. Bestepe, F.-Weather Radar Principles, TSMS, 200520. Buyukbas, E., Sireci, O., Hazer, A., Temir, İ., Geçer, C., Macit, A.- Training Material on

Weather Radar Systems, TSMS-WMO, 200521. Weipert, A.-Meteor Radar Systems, Gematronik, 200522. Sloan, F.-The New EEC Weather Systems, EEC, 200523. Pudas, P, N.-Vaisala Weather Radar, Vaisala, 200524. Yılmazer, C., Slater, G.- Basic Principles of Weather Radar, Esdaş A.Ş.-Radtec

Engineering, 200525. Brenner, F.-Automatic Calibration of Weather Radars, Metstar, 200526. Stolz, W.- Report of the Global Observing System in Region IV, WMO, 200627. Bjørheim, K.-Report of the Global Observing System in Region VI, WMO, 2006 28. Pümpel, H.-Statement of Guidance for Nowcasting and Very Short Range Forecasting,

WMO, 200629. Braswell, R.-Radar Systems, Baron Services, 200630. Radar Feasibility Report for Turkish Radar Network, TSMS, 200631. Project for the New-Generation Weather Radar Monitoring Network in China, CMA; 2008 32. Joe, P., Whetten, F., Scott, J., Whetten, D.-RLAN and Weather Radar Interference Studies,

200833. Technical Specifications for Turkish Radar Network, TSMS, 200834. Holleman, I., Delobbe, L., Zgonc, A.,-Update on the European Weather Rad. Net. (OPERA),

200935. Tristant, P.,-Report on RLAN 5 GHz interference to weather radars in Europe WMO-ITU,

200936. Replies to Questionnaire on Weather Radars prepared by Joe, P., Sireci, O., Ruedi, I.,

CIMO, 2009

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